Visible light communication (VLC) is a new technology for short-range optical wireless communication using visible light in optically transparent media. This technology provides access to several hundred terahertz (THz) of unlicensed spectrum. VLC is immune to the problems of electromagnetic interference and non-interference associated with radio frequency (RF) systems. VLC provides an additional level of security by allowing a user to see the transmission of data across the communication channel. Another benefit of VLC is that it augments and complements existing services (such as illumination, display, indication, decoration, etc.) from existing visible-light infrastructures. A VLC network is any network of two or more devices that engage in VLC.
The IEEE 802.15.7 standard supports multiple applications such as peer-to-peer communication, visible LAN communication, broadcasting/multicasting applications and vehicular applications. The characteristics of the optical sources used for these applications vary greatly, and the switching frequency can range from 100s of KHz (e.g., for a traffic light LED) to 100s of Mbps (e.g., for a laser diode or a resonant-cavity LED). As such, using the clock rate that is supported by two communicating devices would decrease the efficiency. Thus, the IEEE 802.15.7 standard enables support for a variety of optical sources and applications. This requires the support of multiple clock frequencies in the standard as not all optical sources may be able to support all switching frequencies needed to achieve high data rates.
Due to the fact that different optical sources (LEDs) have different switching capabilities, and not all optical sources can support the high clock speeds, there is a need to support multiple clock speeds for VLC.